The habitat of L. acidophilus can be found in many places. This bacterium can be found in animal and human intestinal tracts (for humans it is found in the gastrointestinal tract), soil, water, milk and milk products, plants, silage, and manure.  It is a known fact that Lactobacillus bacteria reproduce very quickly, doubling their population every 20 minutes, at the temperature of approximately 32*C (90*F).